Brake systems of heavy machinery, non-limiting examples of which include wheel loaders and motor graders, generally include mechanism for shifting the transmission into neutral upon braking.
On most commercially available machines, the neutralizer function associated with the brake application is accomplished by providing an electric proximity switch which closes when the brake pedal is depressed a given amount. This electric signal is used by the transmission control to shift the transmission into neutral. When the pedal is released, the proximity switch opens and the transmission control re-engages the transmission. By the time the transmission re-engages, the brakes have been released. See for example, U.S. Pat. No. 3,998,111, issued Dec. 21, 1976 to Blake, and herein incorporated by reference.
One drawback of such a neutralizer control is that it provides poor inching capability in that it does not easily allow the operator to achieve slow, smooth machine movement without running against the torque converter. Consequently, some operators have been known to turn off the neutralizer function, using the standard neutralizer disable switch for all applications. This results in a reduction in service brake life, increased axle oil temperatures, possible reduction in differential and final drive gear and bearing lives, increased fuel consumption and increase in power train heat loads because the operator runs the machine against the torque converter by applying the brakes with transmission in gear.
In an effort to overcome some of the above described disadvantages, a few commercially available machines include operator selectable neutralizer operating modes to accommodate a variety of applications. These selectable modes usually provide two or three discrete brake pedal positions at which the transmission is shifted to neutral and re-engaged. However, these offer only a partial solution, as the correct mode for the application must be selected, and even that mode will not always provide adequate operation for all situations of that application.
Accordingly, the present invention is directed to overcoming one or more of the problems as set forth above.